68 



STRUCTURAL BOTANY 



but takes no important part in the further development; 

 the middle cell ultimately forms the ovum and the two 

 canal-cells ; while the uppermost of the three grows and 

 divides to form the neck (see Fig. 35). The neck is the 

 only part which projects beyond the surface of the cushion. 

 The neck-cell first divides, by two longitudinal walls 

 at right angles to each other, into four cells placed cross- 



a.n. 



n.n. 



n.c. 



FIG. 35. Development of archegonium of Male Fern. A, very 

 young ; a.n, neck of archegonium ; c, central cell ; b, basal 

 cell. B, rather older ; n.c, neck canal. C, nearly ripe ; 

 n.c, canal cells disorganised. A,B,C, in longitudinal section. 

 D, neck seen from above. Magnified about 250 diameters. 

 (After Kny.) 



wise, as seen in surface view (see Fig. 35, D). Each of 

 these four cells then divides up repeatedly by approxi- 

 mately transverse walls, so that the neck is finally made 

 up of four rows of cells. While these divisions are going 

 on, the neck is increasing in length, and at the same 

 time the central cell grows up between the four rows of 

 neck-cells (see Fig. 35, A and B), which separate a little to 



